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A semi-automatic transmission is a "theoretical" multiple-speed
transmission Transmission may refer to: Medicine, science and technology * Power transmission ** Electric power transmission ** Propulsion transmission, technology allowing controlled application of power *** Automatic transmission *** Manual transmission *** ...
where part of its operation is automated (typically the actuation of the
clutch A clutch is a mechanical device that engages and disengages power transmission, especially from a drive shaft to a driven shaft. In the simplest application, clutches connect and disconnect two rotating shafts (drive shafts or line shafts). ...
), but the driver's input would be required to launch the vehicle from a standstill and to manually change gears. Semi-automatic transmissions were exclusively used in motorcycles and are based on conventional manual transmissions or sequential manual transmissions, but use an automatic clutch system. But some semi-automatic transmissions have also been based on standard hydraulic automatic transmissions with torque converters and planetary gearsets. Names for specific types of semi-automatic transmissions include ''clutchless manual'', ''auto-manual'', ''auto-clutch manual'', and ''paddle-shift'' transmissions. These systems facilitate gear shifts for the driver by operating the clutch system automatically, usually via switches that trigger an
actuator An actuator is a component of a machine that is responsible for moving and controlling a mechanism or system, for example by opening a valve. In simple terms, it is a "mover". An actuator requires a control device (controlled by control signal) a ...
or servo, while still requiring the driver to manually shift gears. This contrasts with a preselector gearbox, in which the driver operates the clutch and selects the next gear ratio, but the gear change within the transmission is performed automatically. The first usage of semi-automatic transmissions was in automobiles, increasing in popularity in the mid-1930s when they were offered by several American car manufacturers. Less common than traditional hydraulic automatic transmissions, semi-automatic transmissions have nonetheless been made available on various car and motorcycle models and have remained in production throughout the 21st century. Semi-automatic transmissions with paddle shift operation have been used in various racing cars, and were first introduced to control the electro-hydraulic gear shift mechanism of the
Ferrari 640 The Ferrari 640 (also known as the Ferrari F1-89) was the Formula One racing car with which the Ferrari team competed in the 1989 Formula One World Championship. It was driven by Britain's Nigel Mansell, in his first season with the team, and A ...
Formula One car in 1989. These systems are currently used on a variety of top-tier racing car classes; including Formula One,
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, and touring car racing. Other applications include motorcycles, trucks, buses, and railway vehicles.


Design and operation

Semi-automatics facilitate easier
gear shift A gear stick (rarely spelled ''gearstick''), gear lever (both UK English), gearshift or shifter (both U.S. English), more formally known as a transmission lever, is a metal lever attached to the transmission of an automobile. The term ''gear sti ...
s by removing the need to depress a clutch pedal or lever at the same time as changing gears. Depending on the mechanical build, design, and age of the vehicle, they can use anything from hydraulic,
pneumatic Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
or electric actuators, electrical switches, motors, and processors, or a combination of any such systems, to execute gear shifts on demand when requested by the driver, which is typically initiated when the driver moves the gear stick. Most cars that have a semi-automatic transmission are not fitted with a standard clutch pedal since the clutch is remotely controlled. Similarly, most motorcycles with a semi-automatic transmission are not fitted with a conventional clutch lever on the handlebar.


Clutchless manual transmissions

Most semi-automatic transmissions are based on conventional manual transmissions, but are usually operated with an automatic clutch or another kind of partially automated transmission mechanism. Once the clutch becomes automated, the transmission becomes semi-automatic. However, these systems still require manual gear selection by the driver. This type of transmission is called a ''clutchless manual'' or an ''automated manual''. Most semi-automatic transmissions in older passenger cars retain the normal H-pattern shifter of a manual transmission; similarly, semi-automatic transmissions on older motorcycles retain the conventional foot-shift lever, as on a motorcycle with a fully manual transmission. However, semi-automatics systems in newer motorcycles,
racing car Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organise ...
s, and other types of vehicles often use gear selection methods such as shift paddles near the
steering wheel A steering wheel (also called a driving wheel (UK), a hand wheel, or simply wheel) is a type of steering control in vehicles. Steering wheels are used in most modern land vehicles, including all mass-production automobiles, buses, light and ...
or triggers near the handlebars. Several different forms of automation for clutch actuation have been used over the years, from hydraulic,
pneumatic Pneumatics (from Greek ‘wind, breath’) is a branch of engineering that makes use of gas or pressurized air. Pneumatic systems used in Industrial sector, industry are commonly powered by compressed air or compressed inert gases. A central ...
, and electromechanical clutches to vacuum-operated, electromagnetic, and even
centrifugal clutch A centrifugal clutch is an automatic clutch that uses centrifugal force to operate. The output shaft is disengaged at low rotational speed and engages more as speed increases. It is often used in mopeds, underbones, lawn mowers, go-karts, chainsaws ...
es. Fluid couplings (most commonly and formerly used in early automatic transmissions) have also been used by various manufacturers, usually alongside some form of mechanical friction clutch, to prevent the vehicle from stalling when coming to a standstill or at
idle Idle generally refers to idleness, a lack of motion or energy. Idle or ''idling'', may also refer to: Technology * Idle (engine), engine running without load ** Idle speed * Idle (CPU), CPU non-utilisation or low-priority mode ** Synchronous ...
. A typical semi-automatic transmission design may work by using Hall effect sensors or micro switches to detect the direction of the requested shift when the gear stick is used. These sensors' output, combined with the output from a sensor connected to the gearbox which measures its current speed and gear, is fed into a transmission control unit, electronic control unit,
engine control unit An engine control unit (ECU), also commonly called an engine control module (ECM), is a type of electronic control unit that controls a series of actuators on an internal combustion engine to ensure optimal engine performance. It does this by re ...
, or microprocessor, or another type of electronic control system. This control system then determines the optimal timing and torque required for smooth clutch engagement. The electronic control unit powers an actuator, which engages and disengages the clutch in a smooth manner. In some cases, the clutch is actuated by a servomotor coupled to a gear arrangement for a linear actuator, which, via a hydraulic cylinder filled with
hydraulic fluid A hydraulic fluid or hydraulic liquid is the medium by which power is transferred in hydraulic machinery. Common hydraulic fluids are based on mineral oil or water. Examples of equipment that might use hydraulic fluids are excavators and backhoe ...
from the braking system, disengages the clutch. In other cases, the internal clutch actuator may be completely electric, where the main clutch actuator is powered by an electric motor or
solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
, or even pneumatic, where the main clutch actuator is a pneumatic actuator that disengages the clutch. A clutchless manual system, named the ''
Autostick The name Autostick has been used for a Volkswagen semi-automatic transmission, which is a vacuum-operated automatic clutch system, coupled with a conventional 3-speed manual transmission. The "AutoStick" system designed by Chrysler allows for ma ...
'', was a semi-automatic transmission introduced by Volkswagen for the 1968 model year. Marketed as the ''Volkswagen Automatic Stickshift'', a conventional three-speed manual transmission was connected to a vacuum-operated automatic clutch system. The top of the gear stick was designed to easily depress and activate an electric switch, i.e. when touched by the driver's hand. When pressed, the switch operated a 12-volt
solenoid upright=1.20, An illustration of a solenoid upright=1.20, Magnetic field created by a seven-loop solenoid (cross-sectional view) described using field lines A solenoid () is a type of electromagnet formed by a helix, helical coil of wire whose ...
, which in turn operated the vacuum clutch actuator, thus disengaging the clutch and allowing shifting between gears. With the driver's hand removed from the gearshift, the clutch would re-engage automatically. The transmission was also equipped with a torque converter, allowing the car to idle in gear like with an automatic, as well as stop and start from a standstill in any gear.


Automated manual transmissions

Starting in the late 1990s, automotive manufacturers introduced what is now called an
automated manual transmission The automated manual transmission (AMT) is a type of transmission for motor vehicles. It is essentially a conventional manual transmission but uses automatic actuation to operate the clutch and/or shift between gears. Many early versions of t ...
(AMT), which is mechanically similar to, and has its roots in, earlier clutchless manual transmission systems. An AMT functions in the same way as older semi-automatic and clutchless manual transmissions, but with two exceptions; it is able to both operate the clutch and shift automatically, and does not use a torque converter. Shifting is done either automatically from a transmission control unit (TCU), or manually from either the shift knob or shift paddles mounted behind the steering wheel. AMTs combine the fuel efficiency of manual transmissions with the shifting ease of automatic transmissions. Their biggest disadvantage is poor shifting comfort due to the mechanical clutch being disengaged by the TCU, which is easily noticeable as "jolting". Some transmission makers have tried solving this issue by using oversized synchronizer rings and not fully opening the clutch during shifting—which works in theory, but as of 2007, there have not been any series production cars with such functions. In passenger cars, modern AMTs generally have six speeds (though some have seven) and a rather long gearing. In combination with a smart-shifting program, this can significantly reduce fuel consumption. In general, there are two types of AMTs: integrated AMTs and add-on AMTs. Integrated AMTs were designed to be dedicated AMTs, whereas add-on AMTs are conversions of standard manual transmissions into AMTs. An automated manual transmission may include a fully automatic mode where the driver does not need to change gears at all. These transmissions can be described as a standard manual transmission with an automated clutch and automated gear shift control, allowing them to operate in the same manner as traditional automatic transmissions. The TCU automatically shifts gears if, for example, the engine is
redline Redline refers to the maximum engine speed at which an internal combustion engine or traction motor and its components are designed to operate without causing damage to the components themselves or other parts of the engine. The redline of an en ...
d. The AMT can be switched to a clutchless manual mode wherein one can upshift or downshift using a console-mounted shift selector or paddle shifters. It has a lower cost than conventional automatic transmissions. These transmissions are not to be confused with " manumatic" automatic transmissions, which are marketed under trade names such as ''Tiptronic'', ''Steptronic'', ''Sportmatic'', and ''
Geartronic Geartronic is Volvo Cars' name for its manumatic automatic transmission, similar to Porsche's ''Tiptronic''. It is available in 4-, 5-, 6-, and 8-speed models, and is controlled by a microprocessor. The microprocessor automatically shifts to the n ...
''. While these systems seem superficially similar, they are closer in design to automatic transmissions than manual transmissions.


Sequential manual transmissions

Several semi-automatic transmissions used by motorcycles and racing cars are actually mechanically based on sequential manual transmissions. Semi-automatic motorcycle transmissions generally omit the clutch lever, but retain the conventional heel-and-toe foot shift lever. Semi-automatic motorcycle transmissions are based on conventional sequential manual transmissions and typically use a
centrifugal clutch A centrifugal clutch is an automatic clutch that uses centrifugal force to operate. The output shaft is disengaged at low rotational speed and engages more as speed increases. It is often used in mopeds, underbones, lawn mowers, go-karts, chainsaws ...
. At idle speed, the engine is disconnected from the gearbox input shaft, allowing both it and the bike to freewheel—unlike with torque converter automatics, there is no idle creep with a properly adjusted centrifugal clutch. As the engine speed rises, counterweights within the clutch assembly gradually pivot further outwards until they start to make contact with the inside of the outer housing and transmit an increasing amount of engine power and torque. The effective "bite point" or "biting point" is found automatically by equilibrium, where the power is transmitted through the (still-slipping) clutch is equal to what the engine can provide. This allows relatively fast full-throttle takeoffs (with the clutch adjusted so the engine is at peak torque) without the engine slowing or being bogged down, as well as more relaxed starts and low-speed maneuvers at lower throttle and RPMs.


Usage in passenger cars


1900s—1920s

In 1901, Amédée Bollée developed a method of shifting gears that did not require the use of a clutch and was activated by a ring mounted within the steering wheel. One car using this system was the 1912 Bollée Type F Torpedo.


1930s—1940s

Prior to the arrival of the first mass-produced hydraulic automatic transmission (the
General Motors The General Motors Company (GM) is an American Multinational corporation, multinational Automotive industry, automotive manufacturing company headquartered in Detroit, Michigan, United States. It is the largest automaker in the United States and ...
Hydra-Matic) in 1940, several American manufacturers offered various devices to reduce the amount of clutch or shifting input required. These devices were intended to reduce the difficulty of operating the unsynchronised manual transmissions, or "crash gearboxes", that were commonly used, especially in stop-start driving. An early step towards automated transmissions was the 1933–1935 REO Self-Shifter, which automatically shifted between two forward gears in the "forward" mode (or between two shorter gear ratios in the "emergency low" mode). Standing starts required the driver to use the clutch pedal. The Self-Shifter first appeared in May 1933 and was offered as standard on the Royale and as an option on the Flying Cloud S-4. In 1937, the four-speed Oldsmobile Automatic Safety Transmission was introduced on the
Oldsmobile Six The Oldsmobile Six, also known as the Model 53, 54 and 55 (1913-1915) then a brief cancellation until it reappeared as the Model 37, 37A and 37B (1917-1921) was a top level sedan along with the Oldsmobile Series 40 junior vehicle produced by GM's ...
and Oldsmobile Eight models. It used a planetary gearset with a clutch pedal for starting from a standstill and switching between the "low" and "high" ranges. The Automatic Safety Transmission was replaced by the fully-automatic Hydra-Matic for the 1940 model year. The 1938–1939
Buick Special The Buick Special was an automobile produced by Buick. It was usually Buick's lowest-priced model, starting out as a full-size car in 1936 and returning in 1961 (after a two-year hiatus) as a mid-size. The Special was built for several decades and ...
was available with another Self-Shifter 4-speed semi-automatic transmission, which used a manual clutch for starting from standstill and an automated clutch for gear changes. The 1941
Chrysler Stellantis North America (officially FCA US and formerly Chrysler ()) is one of the " Big Three" automobile manufacturers in the United States, headquartered in Auburn Hills, Michigan. It is the American subsidiary of the multinational automoti ...
M4 Vacamatic transmission was a two-speed manual transmission with an integral underdrive unit, a traditional manual clutch, and a fluid coupling between the engine and the clutch. The two-speed transmission had "high" and "low" ranges, and the clutch was used when the driver wanted to switch between ranges. For normal driving, the driver would press the clutch, select the High range, and then release the clutch. Once the accelerator was pressed, the fluid coupling would engage and the car would begin moving forward, with the underdrive unit engaged to provide a lower gear ratio. At between , the driver would lift off the accelerator and the underdrive unit would disengage. The Vacamatic was replaced by a similar M6 Presto-Matic transmission for the 1946 model year. Similar designs were used for the 1941–1950
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Drive-Master and the ill-fated 1942 Lincoln Liquimatic. Both of these combined a 3-speed manual transmission with automated shifting between the 2nd and 3rd gears, instead of the Vacamatic's "underdrive" unit. The Packard Electro-Matic, introduced in the 1941 Packard Clipper and
Packard 180 The Packard Custom Super Eight One-Eighty was introduced for the 1940 model year (18th series) by the Packard Motor Car Company to replace the discontinued Packard Twelve as their top-of-the-line luxury model. The car was derived from the Packar ...
, was an early clutchless manual transmission that used a traditional friction clutch with automatic vacuum operation, which was controlled by the position of the accelerator.


1950s–1960s

The automotive products manumatic system, available on the 1953 Ford Anglia 100E, was a vacuum-powered automatic clutch system that was actuated by a switch that was triggered whenever the gear stick was moved. The system could control the throttle cable (to keep the engine at the required RPM for the gear change) and vary the rate of clutch engagement. The successive Newtondrive system, available on the 1957–1958 Ford Anglia, also had a provision for choke control. A similar product was the German
Saxomat Saxomat was a type of automatic clutch available as an option on Fiat 1800, Lancia Flaminia, Saab 93, Borgward Isabella, Goliath/Hansa 1100, Auto Union 1000, Ford Taunus, Trabant, other than some models from BMW, Opel, Steyr-Puch, NSU, Glas ...
automatic clutch system, which was introduced in the mid-1950s and available on various European cars. The Citroën DS, introduced in 1955, used a hydraulic system with a hydraulically-operated speed controller and idle speed step-up device to select gears and operate the otherwise conventional clutch. This allowed clutchless shifting with a single
column A column or pillar in architecture and structural engineering is a structural element that transmits, through compression, the weight of the structure above to other structural elements below. In other words, a column is a compression member. ...
-mounted selector, while the driver simultaneously lifted off the accelerator to change gear. This system was nicknamed "Citro-Matic" in the U.S. For the 1962 model year, American Motors introduced the E-Stick, which eliminated the clutch pedal in the
Rambler American The Rambler American is a compact car that was manufactured by the American Motors Corporation (AMC) between 1958 and 1969. The American was the second incarnation of AMC forerunner Nash Motors' compact Rambler that was introduced in 1950 an ...
with standard three-speed manual transmissions. This automatic clutch used engine oil pressure as a hydraulic source and was available for less than $60. Compared to fully automatic transmissions of the time, the E-Stick offered the fuel economy of a stick-shift, with vacuum and electric switches controlling the clutch. The E-Stick three-speed transmission was offered on the larger
Rambler Classic The Rambler Classic is an intermediate sized automobile that was built and sold by American Motors Corporation (AMC) from the 1961 through 1966 model years. The Classic took the place of the Rambler Six and Rambler Rebel V-8 names, which were ...
models, along with an overdrive unit. The system was only available with 6-cylinder engines, and the lack of a clutch proved unpopular, so it was discontinued after 1964. The 1967 Volkswagen WSK (''Wandlerschaltkupplungsgetriebe''; English: ''Torque converter shift/clutch gearbox''), used in the Beetle and
Karmann Ghia The Volkswagen Karmann Ghia is a sports car marketed in 2+2 coupe (1955–1974) and 2+2 convertible (1957–1974) body styles by Volkswagen. Internally designated the Type 14, the Karmann Ghia combined the chassis and mechanicals of the Type 1 ( ...
, was one of the first gearboxes of its kind, with an automatic mechanical clutch and a torque converter. Shifting was done manually by the driver. The automatic mechanical clutch allowed the car to accelerate from a stop, whereas the torque converter enabled it to do so in any gear. Dampening engine vibrations and providing torque multiplication, it functioned as a sort of "reduction gearbox", so the actual mechanical gearbox only needed three forward gears (this is why conventional automatic transmissions with torque converters normally have fewer gears than manual transmissions). The WSK had no "first" gear; instead, the first gear was converted into reverse gear, and the second gear was labeled first (with the third and fourth gears respectively being labeled second and third). The Chevrolet Torque-Drive transmission, introduced on the 1968 Chevrolet Nova and Camaro, is one of a few examples where a semi-automatic transmission was based on a conventional hydraulic automatic transmission (rather than a standard manual transmission). The Torque-Drive was essentially a 2-speed Powerglide automatic transmission without the vacuum modulator, requiring the driver to manually shift gears between "Low" and "High". The quadrant indicator on Torque-Drive cars was "Park-R-N-Hi-1st". The driver would start the car in "1st," then move the lever to "Hi" when desired. The Torque-Drive was discontinued at the end of 1971 and replaced by a traditional hydraulic automatic transmission. Other examples of semi-automatic transmissions based on hydraulic automatics were the Ford 3-speed Semi-Automatic Transmission used in the 1970–1971 Ford Maverick, early versions of Honda's 1976–1988 Hondamatic 2-speed and 3-speed transmissions, and the Daihatsu Diamatic 2-speed transmission used in the 1985–1991 Daihatsu Charade.


Other examples


Usage in motorcycles

An early example of a semi-automatic motorcycle transmission was the use of an automatic centrifugal clutch in the early 1960s by the Czechoslovakian manufacturer Jawa Moto. Their design was used without permission in the 1965 Honda Cub 50, which resulted in Jawa suing Honda for
patent infringement Patent infringement is the commission of a prohibited act with respect to a patented invention without permission from the patent holder. Permission may typically be granted in the form of a license. The definition of patent infringement may v ...
and Honda agreeing to pay royalties for each motorcycle using the design. Other semi-automatic transmissions used in motorcycles include: * Honda's Hondamatic two-speed transmission fitted with a torque converter (which shares its name with several fully-automatic transmissions), as used in its 1976 CB750A, 1977 CB400A Hawk, 1978 CM400A and 1982 CM450A. * Those in various minibikes, including the Amstar Nostalgia 49, Honda CRF50F, Z series, and
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KLX-110, KLX-110R, and KSR110,
KTM 65 SX The KTM 65 SX is a youth motorcycle made by KTM KTM AG (Kraftfahrzeug Trunkenpolz Mattighofen, formerly KTM Sportmotorcycle AG) is an Austrian motorcycle, bicycle and sports car manufacturer owned by Pierer Mobility AG and the Indian manufac ...
,
Suzuki is a Japan, Japanese multinational corporation headquartered in Minami-ku, Hamamatsu, Japan. Suzuki manufactures automobiles, motorcycles, All-terrain vehicle, all-terrain vehicles (ATVs), outboard motor, outboard marine engines, wheelchairs ...
DR-Z50, DR-Z70, and DR-Z125, SSR SR110TR, and Yamaha TT-R50E. * Yamaha used an automatic clutch system called YCCS on motorcycles such as the 2006
Yamaha FJR1300 The Yamaha FJR1300A and FJR1300AE/AS are sport touring motorcycles made by Yamaha Motor Company. Both models have a 1,298 cc inline-four engine. The AE/AS model has an electronically controlled clutch and gear shifting system called YCC-S. Th ...
AE sports-touring. This system can be shifted either with the lever in the traditional position near the left foot or with a switch accessible to the left hand where the clutch lever would go on traditional motorcycles. * The Can-Am Spyder Roadster's SE5 and SE6 5-speed and 6-speed transmissions. * Those in several underbone motorcycles in the 1970s; the
Suzuki FR50 The is an underbone style motorcycle produced by Suzuki from 1974 to the early 1980s. It was very similar in design to the Suzuki FR80 It was powered by a , two stroke, air-cooled, single-cylinder engine which incorporated a self-mixing system ...
,
Suzuki FR80 The is a step through motorcycle, very similar to the Yamaha Motor Company, Yamaha Mate and the Honda Super Cub, that was produced by Suzuki from the early 1970s to the early 1980s. It is powered by an , Two-stroke engine, two-stroke, Air-cooled ...
, and Yamaha Townmate used 3-speed transmissions with a heel-and-toe gear shift. * Some high-performance sport bikes use a trigger-shift system, with a handlebar-mounted trigger, paddle, switch, or button, and an automatically operated clutch. * Some dirt bikes use this system, which is sometimes referred to as an auto-clutch transmission. These include the Honda CRF110F and Yamaha TT-R110E. The conventional motorcycle foot shifter is retained, but the manual hand-clutch lever is no longer required. Semi-automatic transmissions in dirt bikes may be referred to as "automatic" despite a lack of automatic shifting.


Usage in motorsports

Semi-automatic transmissions in
racing car Auto racing (also known as car racing, motor racing, or automobile racing) is a motorsport involving the racing of automobiles for competition. Auto racing has existed since the invention of the automobile. Races of various sorts were organise ...
s are typically operated by shift paddles connected to a designated transmission control unit. The first Formula One car to use a semi-automatic transmission was the 1989
Ferrari 640 The Ferrari 640 (also known as the Ferrari F1-89) was the Formula One racing car with which the Ferrari team competed in the 1989 Formula One World Championship. It was driven by Britain's Nigel Mansell, in his first season with the team, and A ...
. It used hydraulic actuators and electrical solenoids for clutch control and shifting, and was shifted via two paddles mounted behind the steering wheel. Another paddle on the steering wheel controlled the clutch, which was only needed when starting from a standstill. The car won its debut race at the
Brazilian Grand Prix The Brazilian Grand Prix ( pt, Grande Prêmio do Brasil), currently held under the name São Paulo Grand Prix ( pt, Grande Prêmio de São Paulo), is a Formula One championship race which is currently held at the Autódromo José Carlos Pace ...
, but for much of the season suffered from reliability problems. Other teams began switching to similar semi-automatic transmissions; the 1991 Williams FW14 was the first to use a sequential drum-rotation mechanism (similar to those used in
motorcycle transmission A motorcycle transmission is a transmission created specifically for motorcycle applications. They may also be found in use on other light vehicles such as motor tricycles and quadbikes, go-karts, offroad buggies, auto rickshaws, mowers, and oth ...
s), which allowed for a more compact design that required only one actuator to rotate the drum and change gears. A further development was made possible by the introduction of electronic throttle control soon after, which made it possible for the car to automatically rev-match during downshifts. By 1993, most teams were using semi-automatic transmissions. The last F1 car fitted with a conventional manual gearbox, the
Forti FG01 The Forti FG01, also designated Forti FG01-95, was a Formula One car for the 1995 season and was the first car made by Forti. The number 21 seat was taken by rookie Pedro Diniz and the number 22 seat was taken by veteran Roberto Moreno. The team n ...
, raced in 1995. Following concerns about the potential for Formula One cars to shift gears automatically without any driver input, mandatory software was introduced in 1994 that ensured that gear changes only occurred when instructed by the driver. Pre-programmed, computer-controlled, fully-automatic upshifts and downshifts were re-introduced and allowed from
2001 The September 11 attacks against the United States by Al-Qaeda, which Casualties of the September 11 attacks, killed 2,977 people and instigated the global war on terror, were a defining event of 2001. The United States led a Participants in ...
, and were permitted from that year's Spanish Grand Prix, but were banned again in
2004 2004 was designated as an International Year of Rice by the United Nations, and the International Year to Commemorate the Struggle Against Slavery and its Abolition (by UNESCO). Events January * January 3 – Flash Airlines Flight 6 ...
. Buttons on the steering wheel to shift directly to a particular gear (instead of having to shift sequentially using the paddles) are permitted. The 2005
Minardi PS05 The Minardi PS05 is a Formula One racing car used by Minardi F1 Team during the 2005 season. It failed to be much of an improvement over its predecessor, as the team finished last in the standings for the third consecutive season. The car was la ...
,
Renault R25 The Renault R25 was the Formula One car entered by Renault in the 2005 season. The chassis was designed by Bob Bell, James Allison, Tim Densham and Dino Toso with Pat Symonds overseeing the design and production of the car as executive direct ...
, and
Williams FW27 The Williams FW27 was the Formula One car which the Williams team used during the 2005 Formula One season. Design and development Overview Like the Minardi PS05 and the Renault R25, the FW27 utilized a 6-speed gearbox rather than the 7-s ...
were the last Formula 1 cars to use a 6-speed gearbox before the switch to a mandatory 7-speed gearbox for the 2006 season. Since 2014 season, Formula 1 cars currently use mandatory 8-speed paddle-shift gearboxes. The now-defunct
CART A cart or dray (Australia and New Zealand) is a vehicle designed for transport, using two wheels and normally pulled by one or a pair of draught animals. A handcart is pulled or pushed by one or more people. It is different from the flatbed tr ...
Champ Car Series switched from a lever-shift sequential system to a 7-speed paddle-shift system for the 2007 season. This transmission was introduced with the new-for-2007 Panoz DP01 chassis. The rival IndyCar Series introduced their 6-speed semi-automatic paddle-shift system for the 2008 season, also replacing the previous lever-shifted sequential transmission, introduced with the Dallara IR-05 chassis for 2008. IndyCars currently use the Xtrac P1011 sequential transmission, which uses a semi-automatic paddle shift system supplied by Mega-Line called AGS (Assisted Gearshift System). AGS uses a pneumatic gearshift and clutch actuator controlled by an internal transmission control unit. Both the
FIA Formula 2 The FIA Formula 2 Championship is a second-tier single-seater championship organised by the Fédération Internationale de l'Automobile (FIA). Held on racing circuits, the championship was introduced in 2017, following the rebranding of the lo ...
and Formula 3 Championships currently use 6-speed sequential gearboxes with electro-hydraulic operation via shift paddles. Manual control of the multi-plate clutch systems via a lever behind the steering wheel is used to launch the cars.
DTM DTM may refer to: Sport * Deutsche Tourenwagen Masters, a motor-racing series staged annually in Germany since 2000 * Deutsche Tourenwagen Meisterschaft, a motor-racing championship staged in Germany from 1984 to 1995 Computing * Deterministic T ...
currently uses a Hewland DTT-200 6-speed sequential transmission with steering-wheel-mounted shift paddles, which was introduced for the 2012 season with the new rule change. This new system replaced the older lever-shifted sequential transmission, which had been used for the previous 12 seasons (since
2000 File:2000 Events Collage.png, From left, clockwise: Protests against Bush v. Gore after the 2000 United States presidential election; Heads of state meet for the Millennium Summit; The International Space Station in its infant form as seen from ...
).


Usage in other vehicles

Other notable uses for semi-automatic transmissions include: * During the 1940s to 1960s, many small diesel
shunting locomotive A switcher, shunter, yard pilot, switch engine, yard goat, or shifter is a small railroad locomotive used for manoeuvring railroad cars inside a rail yard in a process known as ''switching'' (US) or ''shunting'' (UK). Switchers are not inten ...
s used epicyclic semi-automatic transmissions. For example, the British Rail Class 03 and British Rail Class 04 used the
Wilson-Drewry Self-Changing Gears was a British company, set up and owned equally by Walter Gordon Wilson and John Davenport Siddeley, to develop and exploit the Wilson or pre-selector gearbox. Self-Changing Gears designed, built and licensed transmissions for ...
CA5 R7 transmission. * The Sinclair S.S.S. Powerflow, used from the 1950s to the early 1960s in Huwood-Hudswell diesel mining locomotives, the
British Rail Class D2/7 British Rail Class D2/7 was a locomotive commissioned by British Rail in England. It was a diesel powered locomotive in the pre- TOPS period built by Hudswell Clarke with a Gardner engine. The mechanical transmission, using a scoop control ...
and the British Rail Class D2/12. The Powerflow design is of the layshaft type with constant-mesh gears and dog clutch engagement, allowing it to provide seamless power delivery during upshifts. This transmission was also used in some road vehicles. * The Self-Changing Gears Pneumocyclic, an epicyclic transmission built in the United Kingdom from the 1960s to the 1980s. Using a similar design to the company's previous preselector gearboxes, the Pneumocyclic transmission was used in several buses, such as the Leyland Leopard, Panther, and Tiger. It was also fitted to several thousand British diesel railcars during this time. * All-terrain vehicles, such as the Honda ATC185, Honda ATC200, Honda TRX90X and TRX250X (Honda SportClutch), Suzuki LT125D Quadrunner (also known as the Suzuki QuadRunner 125), Suzuki LT 230, Suzuki Eiger 400, Yamaha Big Bear 250, 350, and 400, Yamaha Grizzly 80, Yamaha Raptor 80, Yamaha YFB250 Timberwolf, the Yamaha Moto-4 ATV range, and the Yamaha Tri-Moto range. **The Honda Electric Shift Program is used in ATVs such as the 1998 Honda TRX450FE (also called the Foreman 450ES ESP) and first-generation
Honda Rincon The Honda Rincon is a model of small ATVs manufactured by Honda. There have been two models, launched in 2003 and 2006. The vehicle is designed as a recreational all-terrain vehicle (ATV), rather than a utility or sport version. The Rincon model d ...
. Shifting is accomplished by pressing one of the two gear selector arrows on the left handlebar, which activates an electric shifting system.


See also

*
Automated manual transmission The automated manual transmission (AMT) is a type of transmission for motor vehicles. It is essentially a conventional manual transmission but uses automatic actuation to operate the clutch and/or shift between gears. Many early versions of t ...
(AMT) * Automatic transmission (AT) *
Dual-clutch transmission A dual-clutch transmission (DCT) (sometimes referred to as a twin-clutch transmission) is a type of multi-speed motor vehicle, vehicle Transmission (mechanics), transmission system, that uses two separate clutches for odd and even gear train, g ...
(DCT) * Manumatic *
Shift time Shift time refers to the time interval between gear changes in a transmission. This interval is the time in which power delivery is transferred to the next selected gear, and engine speed is reduced or increased to synchronize the speed of the ne ...


References

{{DEFAULTSORT:Semi-automatic transmission Automotive transmission technologies Automobile transmissions Motorcycle transmissions Mechanical power control